Volume booster with stabilized trim

ABSTRACT

A fluid flow control device includes a body having an inlet connection, an outlet connection, and a discharge port. A supply path extends between the inlet connection and the outlet connection and a booster module is disposed within the body. The booster module includes a control element and an actuator element and defines an exhaust path extending between the outlet connection and the discharge port. A supply port is disposed within the booster module along the supply path between the inlet connection and the outlet connection.

CROSS-REFERENCE TO RELATED APPLICATION

This is a divisional of U.S. application Ser. No. 12/882,549, filed Sep.15, 2010, the entire contents of which are incorporated herein byreference.

FIELD OF THE DISCLOSURE

The present disclosure relates to fluid flow control systems and, moreparticularly, to volume boosters for enhancing control valve performancein fluid flow control systems.

BACKGROUND

Systems for controlling the flow of fluids, such as compressed air,natural gas, oil, propane, or the like, are generally known in the art.These systems often include at least one control valve for controllingvarious flow parameters of the fluid. Typical control valves include acontrol element such as a valve plug, for example, movably disposedwithin the flow path for controlling the flow of the fluid. The positionof such a control element can be controlled by a positioner via apneumatic actuator such as a piston actuator or a diaphragm-basedactuator, as is known in the art. Conventional positioners deliverpneumatic signals via supply fluid to the actuator to stroke the controlelement of the control valve between an open and closed position, forexample. The speed at which a the control valve can stroke partlydepends on the size of the actuator and the flow of supply fluidcontained in the pneumatic signal. For example, larger actuators/controlvalves typically take longer to be stroked when a positioner of equalflow output is used.

Therefore, such systems additionally employ one or more volume boosterslocated between the positioner and the actuator. The volume boosters areused to amplify the volume of supply fluid in relation to the pneumaticsignal sent from the positioner, thereby increasing the speed at whichthe actuator strokes the control element of the control valve.Specifically, it should be understood by one of ordinary skill in theart that the volume booster is connected between the fluid supply andthe valve actuator. Employing a pneumatic restriction in the volumebooster allows large input signal changes to register on the boosterinput diaphragm sooner than in the actuator. A large, sudden change inthe input signal causes a pressure differential to exist between theinput signal and the output of the booster. When this occurs, thebooster diaphragm moves to open either a supply port or an exhaust port,whichever action is required to reduce the pressure differential. Theport remains open until the difference between the booster input andoutput pressures returns to within predetermined limits of the booster.A booster adjustment device may be set to provide for stable operation;(i.e. signals having small magnitude and rate changes pass through thevolume booster and into the actuator without initiating boosteroperation).

However, conventional booster trim is susceptible to flow inducedvibration. This vibration destabilizes the booster and often results inan audible “honking” noise being emitted from the booster. Typicallythis occurs at low lifts when the plug is near the seat and thevibration may occur in three-dimensional axes. This instability canhappen when the booster is supplying air or when the booster isexhausting air. Such vibration or instability degrades the accuracy withwhich the booster can deliver a desired flow rate and causes acceleratedwear of the booster trim components. This unsteady flow rate results ina variable or changing actuator velocity, which is highly undesirable.

Additionally, there are numerous applications where high capacity volumeboosters are required (i.e. systems requiring volume boosters providingat least a maximum flow capacity (Cv) of seven (7.0)). Such largecapacity systems may be designed with multiple volume boosters.Additionally, to maintain the large Cv, large diameter tubing isrequired (i.e. tubing that is at least 1″ in diameter).

Conventional volume boosters attach to the actuator via pipe componentssuch as nipples, tees, and crosses. Control valve assemblies for largecapacity systems may also use external brackets to mount the volumebooster to the actuator. Such existing systems (i.e. systems that usepipe components are structural or mounting members) often require longlengths of tubing to connect the multiple volume boosters. In manyapplications, vibration is common. Thus, the number of boosters and theconventional connection methods make typical high flow capacity actuatorassemblies susceptible to vibration induced failures resulting from thecyclic motion induced during operation. That is, large actuatorapplications, where multiple volume boosters and/or large Cv volumeboosters are required, current state of the art mounting systems areinsufficient to stabilize the volume boosters in seismically activeapplications (i.e. the mounting configuration is dependent on thestructural integrity of the tubing and generally do not minimize themoment of the volume booster in relation to the actuator). That is, longtubing runs associated with multiple volume booster applications andconventional bracketing or mounting are very susceptible to the cyclicstresses produced by system vibration. Furthermore, in applicationswhere high flow capacity is required traditional large diameter tubingis heavy and difficult to bend to make efficient connections leading tolong tubing runs and further subjecting traditional mounting brackets tovibration induced failures as well.

SUMMARY

One embodiment of the present disclosure provides a fluid flow controldevice, comprising a body comprising an inlet connection, an outletconnection, and a discharge port; a supply path extending between theinlet connection and the outlet connection; a booster module disposedwithin the body comprising a control element and an actuator element anddefining an exhaust path extending between the outlet connection and thedischarge port and a supply port disposed within the booster modulealong the supply path between the inlet connection and the outletconnection; and at least a first damping means operatively connected tothe booster module.

In one embodiment, the fluid flow control device further comprises asecond damping means operatively coupled to the booster module.

In one embodiment, the first damping means is comprised of at least oneof a first elastomeric ring or a first dashpot.

In one embodiment, the second damping means is comprised of at least oneof a second elastomeric ring or a second dashpot.

In one embodiment, the first damping means is affixed to the actuationelement by an attachment device.

In one embodiment, the actuation element comprises a diaphragm assemblydefining an exhaust port disposed along the exhaust path between theoutlet port and the discharge port, the diaphragm assembly adapted fordisplacement between a closed position, wherein the exhaust port is insealing engagement with the exhaust plug of the control element to closethe exhaust path, and an open position, wherein the exhaust port isspaced from the exhaust plug of the control element to open the exhaustpath, wherein the control element comprises a stem, a supply plug, andan exhaust plug, the control element adapted for displacement between aclosed position, wherein the supply plug is in sealing engagement withthe supply port to close the supply path, and an open position, whereinthe supply plug is spaced from the supply port to open the supply path,the stem of the control element including a central portion extendingbetween the supply and exhaust plugs and a guide portion extending awayfrom the supply plug in a direction opposite the exhaust plug, the guideportion of the stem slidably disposed within a guide bore carried by thebody, the guide bore being vented to an inlet chamber of the body, theinlet chamber being defined between the inlet port and the supply port.

In one embodiment, the biasing assembly is disposed between thediaphragm assembly and the body, the biasing assembly comprising aseating cup and a spring, the seating cup slidably disposed within aseating bore defined in the body providing an annular space about theseating cup, and the spring disposed in the seating cup and biasing theseating cup and the diaphragm assembly away from the body.

In one embodiment, the supply trim component threadably connected to thebody at a location opposite the control member from the diaphragmassembly, the supply trim component defining a blind bore thatconstitutes the guide bore slidably receiving the guide portion of thestem of the control element.

In one embodiment, the first elastomeric ring is disposed between theseating cup and the seating bore.

In one embodiment, the seating bore is vented to a signal chamber thatis disposed between the diaphragm assembly and the body via the annularspace and wherein the seating cup defines at least one opening definingthe vent between the seating bore and the signal chamber.

In one embodiment, the seating cup includes a bottom wall and asidewall, wherein the at least one opening is defined through thesidewall.

In one embodiment, the at least one opening is defined through thesidewall of the seating cup at a location between the bottom wall of theseating cup and the second elastomeric ring.

In one embodiment, the first elastomeric ring disposed between the guideportion of the stem and the guide bore;

In one embodiment, the supply trim component threadably connected to thebody at a location opposite the control member from the diaphragmassembly, the supply trim component defining a blind bore thatconstitutes the guide bore slidably receiving the guide portion of thestem of the control element.

In one embodiment, the supply trim component includes at least oneopening defining the vent between the guide bore and the inlet chamberof the body and the at least one opening in the supply trim componentcommunicates with the blind bore at a location that is opposite thefirst elastomeric ring from the supply plug of the control element.

In one embodiment, the body comprising an inlet connection, an outletconnection, and a discharge port. A supply path extending between theinlet connection and the outlet connection. A booster module disposedwithin the body comprising a control element and an actuator element anddefining an exhaust path extending between the outlet connection and thedischarge port and a supply port disposed within the booster modulealong the supply path between the inlet connection and the outletconnection, the booster module operating from a quiescent state havingthe supply and exhaust paths substantially closed.

In one embodiment, the fluid flow control device comprises at least afirst damping means operatively connected to the booster module.

In one embodiment, the fluid flow control device further comprises asecond damping means operatively coupled to the booster module.

In one embodiment, the first damping means is comprised of at least oneof a first elastomeric ring or a first dashpot.

In one embodiment, the second damping means is comprised of at least oneof a second elastomeric ring or a second dashpot.

In one embodiment, the first damping means is affixed to the actuationelement by an attachment device.

In one embodiment, the actuation element comprises a diaphragm assemblydefining an exhaust port disposed along the exhaust path between theoutlet port and the discharge port, the diaphragm assembly adapted fordisplacement between a closed position, wherein the exhaust port is insealing engagement with the exhaust plug of the control element to closethe exhaust path, and an open position, wherein the exhaust port isspaced from the exhaust plug of the control element to open the exhaustpath, wherein the control element comprises a stem, a supply plug, andan exhaust plug, the control element adapted for displacement between aclosed position, wherein the supply plug is in sealing engagement withthe supply port to close the supply path, and an open position, whereinthe supply plug is spaced from the supply port to open the supply path,the stem of the control element including a central portion extendingbetween the supply and exhaust plugs and a guide portion extending awayfrom the supply plug in a direction opposite the exhaust plug, the guideportion of the stem slidably disposed within a guide bore carried by thebody, the guide bore being vented to an inlet chamber of the body, theinlet chamber being defined between the inlet port and the supply port.

In one embodiment, the fluid actuator; a positioner; a volume booster;the volume booster having a plurality of mounting surfaces in agenerally rectangular arrangement about a longitudinal axis Z adapted tooperatively couple the volume booster to the actuator.

In one embodiment, the plurality of mounting surfaces defines acube-shaped volume on a lower portion of the volume booster.

In one embodiment, the mounting plate is adapted to slidably attach thevolume booster to the actuator.

In one embodiment, the mounting plate substantially reduces the couplingmoment of the volume booster to the actuator.

In one embodiment, the tubing guide is operatively connected to at leastone of the plurality of mounting surfaces.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic representation of a single-acting spring anddiaphragm actuator assembly including a volume booster constructed inaccordance with the principles of the present disclosure;

FIG. 2 is a side cross-sectional view of one embodiment of a volumebooster constructed in accordance with the principles of the presentdisclosure;

FIG. 3 is a detail view of the volume booster of FIG. 2 taken fromcircle III in FIG. 2;

FIG. 4 is a detail view of the volume booster of FIG. 2 taken fromcircle IV in FIG. 2;

FIG. 5 is a detail view of a unitary booster module of a volume boosterconstructed in accordance with the principles of the present disclosure;

FIG. 6A is a perspective view of one embodiment of a volume boosterconstructed in accordance with the principles of the present disclosure;

FIG. 6B is a perspective view of a volume booster constructed inaccordance with the principles of the present disclosure; and

FIG. 7 is a schematic representation of a double-acting piston actuatorassembly including multiple volume boosters constructed in accordancewith the principles of the present disclosure.

DETAILED DESCRIPTION

The examples, i.e., embodiments, described herein are not intended to beexhaustive or to limit the scope of the invention to the precise form orforms disclosed. Rather, the following description has been chosen toprovide examples of the one or more preferred embodiments to thosehaving ordinary skill in the art.

FIG. 1 provides a schematic representation of a single-acting spring anddiaphragm actuator assembly 10 constructed in accordance with theprinciples of the present disclosure. Specifically, the actuatorassembly 10 comprises an actuator 12, a positioner 14, and a volumebooster 16. In the disclosed embodiment, the actuator assembly 10 isalso illustrated as being fluidly coupled to a regulator 18. Theactuator 12 is adapted to be operably connected to a control valve (notshown) equipped with a movable control element for controlling the flowof a fluid through a system such as a fluid distribution or other fluidmanagement system, for example.

Still referring to FIG. 1, the volume booster 16 includes an inletconnection 30, a outlet connection 32, a control connection 34, and adischarge port 36. The positioner 14 includes an inlet 38 and an outlet40. The actuator 12 includes a actuator supply port 42. The actuator 12,the positioner 14, the volume booster 16, and the regulator 18communicate with each other via a plurality of fluid lines.Specifically, the regulator 18 is in fluid communication with thepositioner 14 and the volume booster 16 via a supply line L1, which issplit into a first supply line L1′ and a second supply line L1″. Theoutlet 40 of the positioner 14 is in fluid communication with thecontrol connection 34 of the volume booster 16 via an output signal lineL2. The outlet connection 32 of the volume booster 16 is in fluidcommunication with the actuator supply port 42 of the actuator 12 via acontrol line L3.

As will be described in more detail, the first supply line L1′ isadapted to deliver a supply pressure to the inlet 38 of the positioner14 and the second supply line L1″ is adapted to deliver a supplypressure to the inlet connection 30 of the volume booster 16. The supplypressure can be provided to the supply line L1 via the regulator 18 froma pressure source such as a compressor, for example. Additionally, thepositioner 14 is adapted to deliver a pneumatic control signal to thevolume booster 16 via the output signal line L2 for controlling theoperation of the actuator 12.

For example, based on an electrical signal received from a controller 20via an electrical connection E1, the positioner 14 transmits a pneumaticsignal to the control connection 34 of the volume booster 16 via theoutput signal line L2. The pneumatic signal passes through the volumebooster 16 to drive the actuator 12 to actuate the control valve (notshown). Typically, the positioner 14 is adapted to generate a pneumaticsignal of a relatively modest flow. Therefore, depending on the size ofthe actuator 12 and/or the desired speed at which the actuator 12 is tostroke the control valve, the volume booster 16 can operate to amplifythe pneumatic signal with additional fluid flow sourced from the supplyline L1, as will be described.

In the embodiment depicted in FIG. 1, the actuator 12 includes a fail-upactuator comprising a diaphragm 22 and a spring 24 contained within adiaphragm casing 26. The diaphragm casing 26 is formed from an uppercasing 26 a and a lower casing 26 b creating an upper cavity 25 a and alower cavity 25 b about diaphragm 22, respectively. The spring 24 isdisposed in the lower cavity 25 b of the casing 26 and biases thediaphragm 22 upward. Therefore, when the positioner 14 sends a pneumaticsignal to the volume booster 16 via the output signal line L2, pneumaticflow is introduced into the upper cavity 25 a of the actuator 12,thereby moving the diaphragm 22 downward. This downward movement is thentransferred into a corresponding movement of the control element of theassociated control valve (not shown), as is understood within the art.

Preferably, the casing 26 includes one or more vents 28 such that fluidcontained within the lower cavity 25 b vents out of the casing 26 whenthe diaphragm 22 moves downward. Such venting facilitates the movementof the diaphragm 22 in either the upward or downward direction. Tostroke the actuator 12 upward, the positioner 14 vents the pneumaticsignal to the volume booster 16 such that the spring 24 moves thediaphragm 22 upward. As the diaphragm 22 moves upward, the pressurebuilt up in the upper cavity 25 a of the casing 26 exhausts to theatmosphere via the control line L3, the discharge port 36 of the volumebooster 16 and vent 28 draws in air to the lower casing 26 b Thisexhausting to the atmosphere facilitates the movement of the diaphragm22 in the upward direction.

With reference now to FIG. 2, one embodiment of the volume booster 16depicted in FIG. 1 will be described. In general, the volume booster 16includes a body 44, booster module 45 and a booster adjustment device52. The body 44 generally includes a lower portion 54, a cap portion 56,and a spacer portion 58. The booster module 45 generally includes a trimassembly 46, a control element 48, a diaphragm assembly 50, and abiasing assembly 49. The lower portion 54 of the body 44 defines theinlet connection 30 and the outlet connection 32. Additionally, thelower portion 54 defines a supply trim opening 60, an inlet chamber 62,a outlet chamber 64, a intermediate region 66, an exhaust chamber 68,and a bypass passage 69. The intermediate region 66 is disposed betweenthe inlet chamber 62 and the outlet chamber 64 and generally defines acylindrical cavity including a lower web 70 and an upper web 72. Theupper web 72 includes a threaded cylindrical opening receiving acorresponding portion of the trim assembly 46, as will be described.Similarly, the supply trim opening 60 includes a threaded cylindricalopening receiving a portion of the trim assembly 46. The cap portion 56of the body 44 is disposed opposite the spacer portion 58 from the lowerportion 54, thereby affixing the spacer portion 58 between the lowerportion 54 and the cap portion 56, as illustrated. As shown in FIG. 3,the cap portion 56 defines, in part, a seating bore 51 slidablyreceiving at least a portion of the biasing assembly 49.

Referring back to FIG. 2, the trim assembly 46 includes a supply trimcomponent 74 and an exhaust trim component 76. In the disclosedembodiment, the supply trim component 74 includes a cylindrical bushingremovably threaded into the supply trim opening 60 of the lower portion54 of the body 44 of the volume booster 16. In alternative embodiments,the supply trim component 74 could be formed as a single or unitarypiece with the exhaust trim component 76 (as described in detail below)of the body 44 of the volume booster 16. As illustrated in FIG. 2, thesupply trim component 74 includes a skirt portion 80, a hexagonal nutportion 82, and a spring seat 84. Additionally, as illustrated in FIG.4, the supply trim component 74 includes a guide bore 85 having an firstannular space 71. The guide bore 85 slidably receives a portion of thecontrol element 48 within the first annular space 71 to guide thecontrol element 48 and stabilize operation of the device.

With reference to FIG. 4, the guide bore 85 is vented to the supplychamber 62 via an opening 87 formed in the supply trim component 74. Theopening 87, as illustrated, includes a through-bore extending andcommunicating between the guide bore 85 and the supply chamber 62 at anangle relative to a longitudinal axis of the guide bore 85. In otherembodiments, the opening 85 could be configured differently. Withcontinued reference to FIG. 4, the supply trim component 74 furtherdefines a circumferential groove 89 formed in an inner sidewall 85 a ofthe guide bore 85. The groove 89 accommodates an elastomeric ring 91,which can include a lubricated rubber o-ring, for example. As will bedescribed further below, the opening 87 and the elastomeric ring 91cooperate to stabilize operation of the volume booster 16 dampingundesirable vibrations.

Referring back to FIG. 2, the skirt portion 80 includes a generallyhollow cylindrical member extending from the hexagonal nut portion 82into the supply chamber 62 of the lower portion 54 of the body 44. Theskirt portion 80 defines a plurality of passages 86 extending radiallytherethrough. In the depicted embodiment, the passages 86 includecylindrical bores. Thus, the passages 86 extend along an axis that isgenerally perpendicular to an axis of the skirt portion 80. Soconfigured, the skirt portion 80 of the supply trim component 74restricts the flow of fluid through the body 44 from the supply chamber62 to the outlet chamber 64 when the supply port is open (Not Shown).The exhaust trim component 76 includes a cylindrical bushing removablythreaded into the cylindrical opening of the upper web 72 of theintermediate region 66 of the body 44. In other embodiments, the exhausttrim component 76 could be formed as one piece with the body 44. Theexhaust trim component 76 also may include a hexagonal nut portion 88, arestrictor portion 90, a skirt portion 92, and a seating portion 94.

The hexagonal nut portion 88 of the exhaust trim component 76 isdisposed within the exhaust chamber 68 of the body 44 and abuttedagainst the upper web 72. The restrictor portion 90 includes a generallysolid cylindrical member disposed within the cylindrical opening of theupper web 72 and defines a plurality of exhaust passages 96 and acontrol opening 97. In the depicted embodiment, the passages 96 in therestrictor portion 90 include cylindrical bores extending axiallythrough the exhaust trim component 76. The skirt portion 92 extends fromthe restrictor portion 90 into the intermediate region 66 and defines aplurality of windows 98. So configured, the plurality of passages 96 inthe restrictor portion 90 provides constant fluid communication betweenthe outlet chamber 64 and the exhaust chamber 68, via the plurality ofpassages 96 in the restrictor portion 90.

The seating portion 94 of the exhaust trim component 76 includes agenerally cylindrical member disposed within a cylindrical opening ofthe lower web 70 of the body 44. The seating portion 94 defines acentral bore 100 and a valve seat 102. The central bore 100 is definedherein as a “supply port” of the volume booster 16. In the disclosedembodiment, the seating portion 94 also includes an external annularrecess 104 receiving a seal 106 such as an o-ring. The seal 106 providesa fluid tight seal between the seating portion 94 of the exhaust trimcomponent 76 and the lower web 70.

As illustrated in FIG. 2, the control element 48 of the disclosedembodiment of the volume booster 16 includes a control element 48comprising a supply plug 108, an exhaust plug 110, and a stem 112. Thestem 112 includes a central portion 112 a and a guide portion 112 b. Thecentral portion 112 a extends between and connects the supply plug 108to the exhaust plug 110, and is slidably disposed in the control opening97 of the restrictor portion 90 of the exhaust trim component 76. Soconfigured, the exhaust plug 110 is disposed within the exhaust chamber68 of the body 44, and the supply plug 108 is disposed within the supplychamber 62 of the body 44. More specifically, the supply plug 108 isdisposed inside of the skirt portion 80 of the supply trim component 74and is biased away from the supply trim component 74 by a spring 114.The spring 114 is seated against the spring seat 84 of the supply trimcomponent 74. The spring 114 biases the supply plug 108 of the controlelement 48 into engagement with the valve seat 102 of the seatingportion 94 of the exhaust trim component 76, thereby closing the “supplyport” 100. In the disclosed embodiment, each of the supply and exhaustplugs 108, 110 includes a tapered cylindrical body defining afrustoconical seating surface. Other shapes of course could beimplemented to satisfy the intended functions.

Referring to FIG. 4, the guide portion 112 b of the stem 112 is slidablydisposed in the guide bore 85 of the supply trim component 74 such thatthe elastomeric ring 91 is disposed between the guide portion 112 b andthe guide bore 85. So disposed, the elastomeric ring 91 creates frictionbetween the guide portion 112 b of the stem 112 and the guide bore 85such as to eliminate the ability of small vibrations generated in thevolume booster 16 to affect the axial position of the control element48. Moreover, the elastomeric ring 91 can be radially compressed betweenthe guide portion 112 b of the stem 112 and the guide bore 85 such thatthe elastomeric ring 91 serves to center the guide portion 112 b andeliminate vibrations generated in the volume booster 16, which can alsoaffect the lateral position of the stem 112. A first or lower ventopening 87, which vents the guide bore 85, further assists with dampingvibrations by providing an escape for any gas that may otherwisecompress and expand inside of the guide bore 85, wherein uncontrolledcompression and expansion due to vibrations in the system can exertunwanted forces on the stem 112.

That is, the first vent opening 87 and first annular space 71 create arestricted vent that functions as a first air spring or a dashpot toprovide additional damping of the control element 48. The lower ventopening 87 and first annular space 71 form a predetermined fluidrestriction between the guide bore 85 and the supply seat chamber 83.For example, a diameter of the lower vent opening 87 may be 0.035 inchesand the diametric clearance of the first annular space 71 may be 0.024inches. The predetermined fluid restriction creates a transition delay(i.e. establishes a time constant) for fluid being pumped between theguide bore 85 and the supply seat chamber 83. This transition delaycreates the first air spring which may oppose vibrations induced in thecontrol element 48. While the present embodiment of the supply trimcomponent 74 has been described as including both the elastomeric ring91 and the lower vent opening 87, alternative embodiments could includeeither the elastomeric ring 91 or the lower vent opening 87, as eachserve to reduce the effect of vibrations on the position of the controlelement 48.

Referring back to FIG. 2 and as mentioned above, the spacer portion 58of the body 44 of the volume booster 16 is positioned between the capportion 56 and the lower portion 54. Generally, the spacer portion 58includes an annular ring defining a radial through-bore, which comprisesthe discharge port 36 of the volume booster 16. Additionally, the spacerportion 58 defines an axial through-bore 116 in alignment with thebypass passage 69 of the lower portion 54 of the body 44. The dischargeport 36 provides fluid communication between the exhaust chamber 68 ofthe lower portion 54 of the body 44 and the atmosphere, via thediaphragm assembly 50, as will be described.

The diaphragm assembly 50 comprises a floating manifold 120 positionedbetween first and second diaphragms 122, 124. The first diaphragm 122includes a flexible diaphragm made from a known diaphragm material andincludes a peripheral portion 122 a and a central portion 122 b. Theperipheral portion 122 a is compressed between the cap portion 56 andthe spacer portion 58 of the body 44 of the volume booster 16. Theperipheral portion 122 a additionally defines an opening 126 inalignment with the axial through-bore 116 of the spacer portion 58. Thesecond diaphragm 124 similarly includes a flexible diaphragm made from aknown diaphragm material and includes a peripheral portion 124 a and acentral portion 124 b. The peripheral portion 124 a of the seconddiaphragm 124 is compressed between the spacer portion 58 and the lowerportion 54 of the body 44. The peripheral portion 124 a additionallydefines an opening 129 in alignment with the axial through-bore 116 ofthe spacer portion 58. The central portion 124 b further defines acentral opening 131. The manifold 120 is disposed between the centralportions 122 b, 124 b of the first and second diaphragms 122, 124 suchthat an annular passage 127 is defined between the manifold 120 and thespacer portion 58 of the body 44.

The manifold 120 comprises a disc-shaped member movably disposed insideof the spacer portion 58 of body 44. The manifold 120 defines an axialopening 128, an internal cavity 130, and a plurality of radial passages132. The axial opening 128 is aligned with the central opening 131 inthe second diaphragm 124 and is defined herein as an “exhaust port” ofthe volume booster 16. The axial opening 128 is equipped with a seatingmember 135 defining a valve seat 137. The axial opening 128 provides forfluid communication between the exhaust chamber 68 of the lower portion54 of the body 44 and the internal cavity 130 of the manifold 120. Theradial passages 132 provide for fluid communication between the internalcavity 130 of the manifold 120 and the annular passage 127 disposedbetween the manifold 120 and the spacer portion 58 of the body 44. Thecap portion 56 of the body 44 of the volume booster 16 includes thecontrol connection 34 and a threaded bore 138 connected by a fluidpassage 140.

Additionally, the cap portion 56 defines a signal chamber 142 disposedabove the diaphragm assembly 50 and in fluid communication with thecontrol connection 34. The threaded bore 138 accommodates the boosteradjustment device 52, which in one embodiment can include an adjustmentscrew. The booster adjustment device 52 can therefore be adjusted toadjust fluid flow from the control connection 34 to the outlet chamber64. That is, the booster adjustment device 52 creates a pneumaticrestriction between the control connection 34 and the outlet chamber 64.Because of the restriction, large input signal changes at the controlconnection 34 register on the diaphragm assembly 50 of the volumebooster 16 sooner than on the diaphragm 22 of the actuator 12. Forexample, a large, sudden change in the input signal causes a pressuredifferential to exist between the control connection 34 and the outletchamber 64 and activates the volume booster from a quiescent state. Whenthis occurs, the diaphragm assembly 50 moves in opposition to therespective biasing element, as will be described later on, to openeither the supply port or the exhaust port creating either a “inlet”state or an “exhaust” state in the volume booster 16, whichever actionis required to reduce the pressure differential.

As is also depicted in FIG. 2 and as mentioned above, the presentembodiment of the volume booster 16 includes the biasing assembly 49disposed between the diaphragm assembly 50 and the cap portion 56 of thebody 44. Generally, the biasing assembly 49 biases the diaphragmassembly 50 away from the cap portion 56 such that the valve seat 137 ofthe seating member 135 disposed in the axial opening 128 of the manifold120 engages the exhaust plug 110 of the control element 46. Thisengagement closes the exhaust port 128.

With reference to FIG. 3, the biasing assembly 49 includes a spring seat53 and a spring 55. The spring seat 53 comprises a seating cup 57including a bottom wall 59 and a sidewall 61 defining a cavity 63therebetween. The bottom wall 59 further includes an attachment device47, such as a rivet, to fixedly attach the seating cup 57 to thediaphragm assembly 50 via through-hole 77. In one embodiment, thesidewall 61 can be a cylindrical sidewall thereby defining a cylindricalcavity 63. The seating cup 57 is disposed between the cap portion 56 ofthe body 44 and the diaphragm assembly 50 such that the bottom wall 59contacts a portion of the diaphragm assembly 50 and the sidewall 61 isslidably disposed in the seating bore 51 of the cap portion 56. Thespring 55 includes a coil spring disposed in the cavity 63 of theseating cup 57 and in engagement with the bottom wall 59 of the seatingcup 57 and a horizontal terminal end surface 51 a of the seating bore 51in the cap portion 56 of the body 44, as shown. So configured, thespring 55 biases the seating cup 57 and diaphragm assembly 50 away fromthe cap portion 56.

As also shown in FIG. 3, the biasing assembly 49 includes an elastomericring 65 disposed between the sidewall 61 of the seating cup 57 and aninternal sidewall 51 b of the seating bore 51 of the cap portion 56 ofthe body 44. More specifically, the sidewall 61 of the seating cup 57defines a circumferential groove 67 in an outer surface 61 a. The groove67 retains the elastomeric ring 65 and can include a lubricated rubbero-ring. In other embodiments, the grove 67 can be formed in the sidewall51 a of the seating bore 51 for retaining the elastomeric ring 65. Soconfigured, the elastomeric ring 65 provides friction between theseating cup 57 and the seating bore 51 to eliminate small amplitudevibrations generated by the diaphragm assembly 50 during operation.

Additionally, as is also illustrated in FIG. 3, the spring seat 53defines a second or upper vent opening 69 in the sidewall 61 of theseating cup 57. The upper vent opening 69 communicates with the cavity63 in the seating cup 57, and therefore, the seating bore 51 such as toprovide a vent for the seating bore 51 that also communicates with thesignal chamber 142 defined above the diaphragm assembly 50 via a secondannular space 70 between the outer surface 61 a of the sidewall 61 ofthe seating cup 57 and the internal sidewall 51 b of the seating bore51. The upper vent opening 69 and second annular space 70 create arestricted vent that functions as a second air spring or dashpot toprovide additional damping of the control element 48, as described indetail below.

In the disclosed embodiment, the upper vent opening 69 is definedthrough the sidewall 61 of the seating cup 57 at a location between thebottom wall 59 and the groove 67, which retains the elastomeric ring 65.As such, the upper vent opening 69 can also be described as beingdefined through the sidewall of the seating cup 57 at a location betweenthe bottom wall 59 and the elastomeric ring 65. As will be described,this configuration of the upper vent opening 69 works in conjunctionwith the elastomeric ring 65 to provide additional stabilization to thediaphragm assembly 50 by enabling any air that might otherwise betrapped in the cavity 63 to escape.

That is as similarly described above, the upper vent opening 69, inconjunction with the second annular space 70, form a predetermined fluidrestriction between the cavity 63 and the signal chamber 142. Forexample, a diameter of the upper vent opening 69 may be 0.035 inches andthe diametric clearance of the second annular space 70 may be 0.004inches. The predetermined fluid restriction creates a transition delay(i.e. establishes a time constant) for fluid be pumped between thecavity 63 and the signal chamber 142. This transition delay creates asecond air spring that may oppose the motion of the bias assemblythereby providing a damping force that resists such motion, whichsubsequently damps motion of diaphragm assembly 50 and, therefore, thecontrol element 48.

It should further be appreciated that attachment device 47 fixedlyconnects the seating cup 57, and, therefore the second air spring, tothe diaphragm assembly. The direct coupling of the second air spring tothe diaphragm assembly substantially eliminates decoupling of the airspring and the diaphragm assembly 50 during vibration to improve dampingduring unstable operating conditions (i.e. a partial vacuum drawn withinthe cavity 63 may decouple the seating cup 57 from the diaphragmassembly 50). Further, the rigid connection between the seating cup 57and the diaphragm assembly 50 provides guiding and additionaldirectional stability of the diaphragm assembly 50 along a longitudinalaxis defined by the control element 48 via the sidewall 61 of theseating cup 57 and the internal sidewall 51 b of the seating bore 51.

While the present embodiment of the biasing assembly 49 includes boththe elastomeric ring 65 and the upper vent opening 69 and second annularspace 70 to provide stability to the diaphragm assembly 50, alternativeembodiments may include only either the elastomeric ring 65 or the uppervent opening 69 and second annular space 70.

As described above, to actuate the actuator 12 in the downwarddirection, the positioner 14 sends a pneumatic signal to the volumebooster 16. Depending on the flow of the pneumatic signal, the pneumaticsignal either actuates the actuator 12 by itself, or the pneumaticsignal activates the volume booster 16 which is supplemented by fluidsupplied from the regulator 18.

For example, if the pneumatic signal is not sufficient to activate thevolume booster 16, as will be described, the fluid travels from thecontrol connection 34, through the fluid passage 140 in the cap portion56, beyond the booster adjustment device 52, and to the outlet chamber64 of the lower portion 54 of the body 44, via the axial through-bore116 in the spacer portion 58, and the bypass passage 69 in the lowerportion 54 of the body 44. From there, the fluid exits the body 44, viathe outlet connection 32, and enters the actuator supply port 42 of theactuator 12 to move the diaphragm 22 in the downward direction.

While the pneumatic signal actuates the actuator 12, it is also providedto the signal chamber 142 defined by the cap portion 56 of the body 44.Additionally, a steady pneumatic supply is constantly provided to thesupply chamber 62 of the lower portion 54 of the body 44 from theregulator 18 (shown in FIG. 1).

For the sake of description, a pressure differential across the volumebooster 16 is defined as a pressure differential occurring across thediaphragm assembly 50, i.e., between the signal chamber 142 and theexhaust chamber 68. Because the exhaust chamber 68 is in continuousfluid communication with the output chamber 64 of the lower portion 54of the body 44 (via the exhaust passages 96 in the exhaust trimcomponent 76), it can also be said that a pressure differential acrossthe volume booster 16 is defined as a pressure differential occurringbetween the signal chamber 142 and the output chamber 64.

If the pressure differential across the volume booster 16 isinsubstantial, the booster remains in a quiescent or neutral statehaving the supply and exhaust plugs 108, 110 of the control element 48remain in the substantially zero flow or closed positions, as depictedin FIG. 2, whereby each sealingly engages the valve seats 102, 137 ofthe respective supply and exhaust ports 100, 128. So disposed, thediaphragm assembly 50 stays in a static unloaded or neutral position.This position is also assisted by the spring 114 biasing the supply plug108 into engagement with the supply port 100, and the spring 136 biasingthe diaphragm assembly 50 into engagement with the exhaust plug 110. Incontrast, a substantial pressure differential across the volume booster16 is one that is great enough to affect the diaphragm assembly 50,whether up or down, to move the control element 48, relative to theorientation of the volume booster 16 depicted in FIG. 2.

When the controller 20 commands the positioner 14 to stroke the actuator12 upward as depicted in FIGS. 1 and 2, the positioner 14 responds bymodifying the pressure differential across the diaphragm assembly 50 toshift the volume booster 16 from its quiescent state. For example, thepneumatic signal transmitted to the volume booster 16 is decreased. Thiscauses the pressure in the signal chamber 142 to decrease below thepressure in the outlet chamber 64. The diaphragm assembly 50 risesupward while the spring 114 biases the control element 48 upward suchthat the supply plug 108 seals against the valve seat 102 of the supplyport 100, thereby keeping the supply path closed.

With the supply path closed, the control element 48 cannot move upward,but back pressure from the outlet chamber 64 moves the diaphragmassembly 50 further upward against the force of the spring 136. Thismoves the diaphragm assembly 50 away from the exhaust plug 110 of thecontrol element 48 and opens the exhaust port 128 creating an “exhaust”state. With the exhaust port 128 open, the volume booster 16 defines an“exhaust path” between the outlet chamber 64 and the discharge port 36.That is, pressurized fluid in the outlet chamber 64 travels to theexhaust chamber 68 via the passages 96 in the exhaust trim component 76,then to the central cavity 130 of the manifold 120 via the exhaust port128, through the radial passages 132 in the manifold 120, and out of thedischarge port 36 to the atmosphere.

When the controller 20 commands the positioner 14 to stroke the actuator12 downward, the positioner 14 responds by modifying the pressuredifferential across the diaphragm assembly 50 to shift the volumebooster 16 from its quiescent state. For example, during operation, apositive pressure differential condition is achieved when pressure issubstantially greater in the signal chamber 142 than in the exhaustchamber 68 such as when the positioner 14 delivers a high fluid flow tothe control connection 34. This can occur when the controller 20 drivesthe positioner 14 to stroke the actuator 12 downward direction, asdepicted in FIGS. 1 and 2. The high fluid flow forces the diaphragmassembly 50 downward, which moves the control element 48 downward,thereby keeping the exhaust plug 110 closed against the exhaust port 128and moving the supply plug 108 away from the supply port 100.

Thus, the volume booster 16 operates in a “inlet” state and subsequentlyopens a “supply path,” which provides fluid flow from the regulator 18to the actuator 12 via the volume booster 16. Specifically, fluid fromthe regulator 18 flows into the supply chamber 62, then through thesupply port 100 and the outlet chamber 64 to the actuator 12, via theoutlet connection 32. Again, because the outlet chamber 64 is also inconstant fluid communication with the exhaust chamber 68 via the exhaustpassages 96 in the exhaust trim component 76, the pressure in the commoncamber 64 is also registered on the second diaphragm 124 of thediaphragm assembly 50.

When the volume booster 16 operates with either the supply path or theexhaust path open, a fluid is flowing through the device. Uponcompletion of the commanded action, such as upward or downward stroking,the volume booster 16 will return to its quiescent or neutral statehaving the supply and exhaust plugs 108, 110 of the control element 48remain in the substantially zero flow or closed positions, as depictedin FIG. 2. However, during operation, the volume booster may rapidly andtemporarily transition from a “inlet” state to an “exhaust” state. Suchrapid changes in fluid flow often include pressure variations that cancause the various components of the volume booster 16 to undesirablyvibrate. For example, as mentioned above, the fluid flow through thevolume booster 16 can cause the position of the diaphragm assembly 50and/or the control element 48 to undergo small fluctuations. Thesefluctuations in position can further result in the fluid flow generatingan undesirable audible noise under certain operating conditions. Assuch, the presently disclosed volume booster 16 may be advantageouslyequipped with the elastomeric rings 65, 91 disposed around the seatingcup 57 of the biasing assembly 49 and the guide portion 112 b of thestem 112, respectively. These elastomeric rings 65, 91 both serve toalign the respective components and damp the effects of vibrations inthe system and stabilize the system.

Furthermore, the disclosed volume booster 16 may include a first or asecond air spring comprised of an upper and a lower vent opening 69, 87,and a first and second annular clearance 70, 71 in the seating cup 57 ofthe biasing assembly 49 and the supply trim component 74, respectively.As described above, these first and second air springs provide a dashpotfunction to the seating bore 51 and the guide bore 85 to further dampthe effects of vibrations in the volume booster 16. As such, the volumebooster 16 disclosed herein advantageously damps the effects ofvibrations on the diaphragm assembly 50 and/or the control element 48 tosubstantially reduce and/or eliminate undesirable audible noises duringoperation.

While the volume booster 16 described herein includes elastomeric ringsand vent openings for the sliding arrangement of the biasing assembly 49and the guide portion 112 b of the stem 112, an alternative embodimentof the volume booster 16 may only include an elastomeric ring and/orvent for one of the biasing assembly 49 and the stem 112. For example,in one alternative embodiment, the volume booster 16 may include theelastomeric ring 65 and/or the opening 69 in the biasing assembly 49,but not the elastomeric ring 91 and/or the opening 87 in the supply trimcomponent 74. Still further, another alternative embodiment couldinclude the elastomeric ring 91 and/or the opening 87 in the supply trimcomponent 74, but not the elastomeric ring 65 and the opening 69 in thebiasing assembly 49. Any of the foregoing alternatives would reducevibrations by providing at least some degree of damping to the volumebooster 16 that would otherwise not be present.

Furthermore, while the seating cup 57 and supply trim component 74 haveeach been described as having one vent opening 69, 87, respectively, inalternative embodiments, these components could include more than oneopening performing the venting function. Similarly, either or both ofthe biasing assembly 49 and the supply trim component 74 could includemore than just the single elastomeric rings 67, 91 depicted in thefigures.

In another embodiment, referring to FIG. 5, the trim assembly 246includes a unitary supply exhaust trim component 276. In the disclosedembodiment, the supply exhaust trim component 276 includes a cylindricalspring seat 274 removably threaded into the supply exhaust trim opening260. Additionally, as illustrated in FIG. 5, the supply exhaust trimcomponent 276 includes a guide bore 285 having an annular space 271. Theguide bore 285 slidably receives a portion of the control element 248within the annular space 271 to guide the control element 248 andstabilize operation of the device. The spring seat 274 preferablyincludes a through-hole 251 to eliminate any pneumatic resistancepresented by the movement of the control element 248 within the guidebore 285. Additionally, an alternate embodiment for the upper air springis illustrated.

As is also depicted in FIG. 5, a biasing assembly 249 is disposedbetween a diaphragm assembly 250 and a cap portion 256 of the body 244.Generally, the biasing assembly 249 biases the diaphragm assembly 250away from the cap portion 256 such that the valve seat 237 of theseating member 235 disposed in the axial opening 228 engages the exhaustplug 210 of the control element 246. This engagement closes the exhaustport 228.

With reference to FIG. 5, the biasing assembly 249 includes a springseat 253 and a spring 255. The spring seat 253 comprises a seating cup257 including a bottom wall 259 and a sidewall 261 defining a cavity 263therebetween. The seating cup 257 is fixedly attach to the diaphragmassembly 250. In one embodiment, the sidewall 261 can be a cylindricalsidewall thereby defining a cylindrical cavity 263. The seating cup 257is disposed between the cap portion 256 of the body 244 and thediaphragm assembly 250 such that the bottom wall 259 contacts a portionof the diaphragm assembly 250 and the sidewall 261 is slidably disposedin the seating bore 251 of the cap portion 256. The spring 255 includesa coil spring disposed in the cavity 263 of the seating cup 257 and inengagement with the bottom wall 259 of the seating cup 257 and ahorizontal terminal end surface 251 a of the seating bore 251 in the capportion 256 of the body 244, as shown. So configured, the spring 255biases the seating cup 257 and diaphragm assembly 250 away from the capportion 256.

As also shown in FIG. 5, the biasing assembly 249 includes anelastomeric ring 265 disposed between the sidewall 261 of the seatingcup 257 and an internal sidewall 251 b of the seating bore 251 of thecap portion 256 of the body 244. More specifically, the sidewall 261 ofthe seating cup 257 defines a circumferential groove 267 in an outersurface 261 a. The groove 267 retains the elastomeric ring 265 and caninclude a lubricated rubber o-ring. In other embodiments, the grove 267can be formed in the sidewall 251 a of the seating bore 251 forretaining the elastomeric ring 265. So configured, the elastomeric ring265 provides friction between the seating cup 257 and the seating bore251 to eliminate small amplitude vibrations generated by the diaphragmassembly 250 during operation.

Additionally, as is also illustrated in FIG. 5, the seating bore 251defines a second or upper vent opening 269 in the sidewall 261 of theseating bore 251. The upper vent opening 269 communicates with thecavity 263 in the seating cup 257 to provide a vent for the seating bore251 above the diaphragm assembly 250. The upper vent opening 269 createsa restricted vent that functions as an air spring or dashpot to provideadditional damping of the control element 248, as described in detailbelow.

In the disclosed embodiment, the upper vent opening 269 is definedthrough the sidewall 261 of the seating bore 251 at a location above theseating cup 257 and the groove 267, which retains the elastomeric ring265. This configuration of the upper vent opening 269 works inconjunction with the elastomeric ring 265 to provide additionalstabilization to the diaphragm assembly 250 by enabling any air thatmight otherwise be trapped in the cavity 263 to escape.

That is as similarly described above, the upper vent opening 269 forms apredetermined fluid restriction useful in stabilizing the volumebooster. For example, a diameter of the upper vent opening 269 may be0.035 inches. The predetermined fluid restriction creates a transitiondelay (i.e. establishes a time constant) for fluid be pumped between thecavity 263 and the signal chamber 142. This transition delay creates asecond air spring that may oppose the motion of the bias assemblythereby providing a damping force that resists such motion, whichsubsequently damps motion of diaphragm assembly 250 and, therefore, thecontrol element 248, which provides additional stability in the volumebooster 216.

With reference now to FIGS. 6A and 6B and as described above, the lowerportion 54 of the volume booster 16 further includes a plurality ofmounting surfaces 27 a, 27 b, 27 c, 27 d in a generally rectangulararrangement about a longitudinal axis Z, thereby defining a cube-shapedvolume on the lower portion 54. The mounting surfaces 27 a-d are adaptedto operatively couple to a mounting plate 23 that may slidably attachthe volume booster 16 to the actuator 12, as will be described in detailbelow. The lower portion 54 may include multiple through holes (notshown) to couple the volume booster 16 to the mounting plate 23. Forexample, the mounting plate 23 may include threaded holes 31 a-31 d tothreadably attach the volume booster 16 to the mounting plate viafasteners 29 a-d. As depicted in FIG. 6A, the mounting plate 23 mayaccommodate various mounting positions or alternate types of actuatorsvia slotted holes 33 a and 33 b on the mounting plate 23. Specifically,the slotted holes 33 a-b provide volume booster/actuator assembly suchthat the supply tubing can be close coupled with minimal bends tosubstantially reduce the length of tubing and reduce the coupling momentof the volume booster 16 to the actuator. Additionally, the mountingplate maybe of a variety of geometries such as square, rectangular,L-shaped, which may be dependent upon the type of actuator or themounting location, as long as the mounting plate is adapted d thesubstantially reduce the coupling moment of the volume booster inrelation to the actuator. It should be appreciated that the volumebooster 16 may also directly attach to an actuator without the need touse a mounting plate, as previously described. For example, the actuatormay include a mounting pad that permits the volume booster to bedirectly fastened or bolted to the actuator.

Further, as depicted in FIG. 6B, at least one of the mounting surfaces27 a-d may include a tubing mount 39 to guide and stabilize additionaltubing, such as the instrument or control tubing. The tubing mount 39may include a clamp or block arrangement to directly couple the controltubing to the actuator via the mounting surfaces 27 a-d viathrough-holes. The embodiment depicted provides tubing connections thatare substantially minimized in length. Such tubing arrangements reducecost and enhance resistance to vibration induced failures and may beconfigured to guide a single tubes or multiple tubes adjacent to thevolume booster 16.

Referring now to FIG. 7, a perspective view of a double-acting pistonactuator assembly 210 constructed in accordance with the principles ofthe present disclosure is illustrated. Specifically, the actuatorassembly 210 comprises an actuator 212, a positioner 214, and volumebooster(s) 216 a-f. The actuator 212 is adapted to be operativelycoupled to a control valve (not shown) equipped with a movable controlelement for controlling the flow of a fluid through a system such as afluid distribution or other fluid management system, for example. Themultiple volume booster(s) 216 a-f include corresponding inletconnections 230 a, 230 b, 230 c (not shown), 230 d, 230 e, 230 f, outletconnections 232 a (not shown), 232 b, 232 c (not shown), 232 d, 232 e,232 f, control connections 234 a, 234 b, 234 c (not shown), 234 d, 234e, 234 f, and discharge ports 236 a (not shown), 236 b, 236 c (notshown), 236 d, 236 e, 236 f. The positioner 214 includes a fluid supplyinlet (not shown) and dual outputs 240 a and 240 b to drive thedouble-acting piston actuator 212 via the volume booster(s) 216 a-f. Theactuator 212 includes lower actuator supply ports 242 a, 242 b, and 242c and upper actuator supply ports 242 d, 242 e and 242 f to receive orexhaust a pneumatic signal for the volume booster(s) 216 a-f. Theactuator 212, the positioner 214, the volume boosters 116 a-fcommunicate via a plurality of fluid lines. The outlets 240 a-b of thepositioner 214 are in fluid communication with the control connections234 a-f of the volume boosters 216 a-f via an output signal lines L2′and L2″. The outlet connections 232 a-f of the volume boosters 216 a-fare in fluid communication with the actuator supply ports 242 a-f of theactuator 212 via the fluid output lines L3′, L3″, L3′″ (not shown) andL4′, L4″, L4′″. The volume booster(s) 216 a-f may be coupled to thefluid supply via supply connections 221 a, 221 b, and 221 c. Aspreviously described, large valve applications require high capacityboosters, which in turn require large diameter tubing to maintain thelarge Cv. The disclosed embodiment provides a tightly coupled high flowcapacity booster arrangement that is slidably coupled to the actuator tosubstantially reduce vibration-related failures.

That is, the arrangement described above preferably attaches the boosterto the actuator such that the booster outlet connection can be “on axis”with the large diameter tubing and actuator port connecting the boosterto either an upper or lower actuator ports. It should be appreciatedthat such a connection both minimizes the overall length of tubingrequired to connect the volume boosters to the actuator andsubstantially eliminates tubing bends to provide close coupling of thevolume booster to the actuator. This significantly reduces the overallmoment of the volume booster with respect to the actuator therebysubstantially reducing the effect of vibration-induced cyclic stresseson the volume booster and its corresponding tubing.

In view of the foregoing, it should be appreciated that the scope of theinvention is neither limited to the specific embodiment described withreference to the figures, nor to the various alternative embodimentsdescribed herein, but rather, to any embodiment that encompasses thespirit of the invention as defined by the following claims.

What is claimed:
 1. A actuator assembly, comprising: a fluid actuator; apositioner; a volume booster having a main inlet connection defining aninlet and a main outlet connection defining an outlet; the volumebooster having a plurality of mounting surfaces in a generallyrectangular arrangement about a longitudinal axis adapted to operativelycouple the volume booster to the actuator, the plurality of mountingsurfaces defining at least a portion of an exterior perimeter of a lowerportion of the volume booster, wherein the plurality of mountingsurfaces defines a cube-shaped volume on the lower portion of the volumebooster, and wherein the lower portion defines the main inlet connectionand the main outlet connection of the volume booster; and a mountingplate having a plate-shaped portion removably secured to one of theplurality of mounting surfaces of the volume booster, the mounting platebeing adapted to slidably attach the volume booster to the actuator,wherein only one of the main inlet connection or the main outletconnection extends through a first one of the plurality of mountingsurfaces such that no other inlet or outlet passage is disposed throughthe first one of the plurality of mounting surfaces, and wherein each ofa second one, a third one, and a fourth one of the plurality of mountingsurfaces includes at most a single inlet passage or a single outletpassage.
 2. The device of claim 1, wherein the mounting platesubstantially reduces a coupling moment of the volume booster to theactuator.
 3. The device of claim 1, wherein a tubing guide isoperatively connected to at least one of the plurality of mountingsurfaces.